Disconnect the fuel rail from the injectors and pump fuel through it into a tray (you can burn this in a lawn mower or something).
This might also be a great time to get those injectors flow tested particularly, since you're using an FMU (yes they work but when they don't the motor is usually a total loss). New O-rings and pintle caps are also a great idea but if you send them in for flow testing, I think they do this too (be sure to ask).
Look on-line for the place nearest you that can do this. Many engine machine shops have this capability.
What fuel pump did you end up with? I sorta lost track.